Watching the Waters

 Scientists believe ocean currents and natural cycles are temporarily offsetting a sea level rise in the Pacific Ocean. Photograph: Ray Collins/Barcroft Media

Scientists believe ocean currents and natural cycles are temporarily offsetting a sea level rise in the Pacific Ocean. Photograph: Ray Collins/Barcroft Media

Over the past century, the burning of fossil fuels and other human and natural activities has released enormous amounts of heat-trapping gases into the atmosphere. These emissions have caused the Earth’s surface temperature to rise, and the oceans absorb about 80 percent of this additional heat. As per a recent update from a panel of NASA scientists, sea levels worldwide rose an average of nearly 3 inches (8 cm) since 1992, the result of warming waters and melting ice.

The rise in sea levels is linked to three primary factors, all induced by this ongoing global climate change. One of them is thermal expansion, a phenomenon where water expands when it heats up. About half of the past century’s rise in sea level is attributable to warmer oceans simply occupying more space.Melting of glaciers and polar ice caps is another factor. Persistently higher temperatures caused by global warming have led to greater-than-average summer melting as well as diminished snowfall due to later winters and earlier springs. Increased heat is also causing the massive ice sheets that cover Greenland and Antarctica to melt at an accelerated pace.

In 2013, a United Nations panel predicted sea levels would rise from 1 to 3 feet (0.3 to 0.9 meters) by the end of the century. The new research shows that sea level rise most likely will be at the high end of that range, said University of Colorado geophysicist Steve Nerem.

Sea levels are rising faster than they did 50 years ago and “it’s very likely to get worse in the future,” Nerem said.

The changes are not uniform. Some areas showed sea levels rising more than 9 inches (25 cm) and other regions, such as along the U.S. West Coast, actually falling, according to an analysis of 23 years of satellite data.

“People need to understand that the planet is not only changing, it’s changed,” NASA scientist Tom Wagner told reporters on a conference call.

“If you’re going to put in major infrastructure like a water treatment plant or a power plant in a coastal zone … we have data you can now use to estimate what the impacts are going to be in the next 100 years,” Wagner said.

Read more here.

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